Subdivision Surface and Knife Project. Blender 2.8
Ok, the problem you mentioned in the comments is because of these little straggler vertices that aren't connected to the mesh like the others.



So to fix that you can start by deleting this ring of faces:



Next, you create a new circle, place it where you want the hole, select the circle and the rim of the guitar created by the deleting of faces, hit ctrl-E, and select "bridge Edge loops".

And here is the result:



It's definitely not as pretty, but there doesn't seem to be any intersections or anything, and it does get the problem fixed.  Hope that helps.